system: show the hardware model on the System page

machine.machine_name is already reported in /information.json as hw_ver;
surface it read-only on the System Settings page so the exact build
target is visible in the UI, without adding a redundant JSON field.

html/i18n.js

@@ -138,6 +138,7 @@ var LANG = {
     sys_tab_console: 'Console',
     sys_heading: 'System Settings',
     sys_ip: 'IP address:',
+    sys_model: 'Model:',
     sys_hostname: 'Hostname:',
     sys_apply: 'Apply',
     sys_netmask: 'Netmask:',
@@ -319,6 +320,7 @@ var LANG = {
     sys_tab_console: 'コンソール',
     sys_heading: 'システム設定',
     sys_ip: 'IP アドレス:',
+    sys_model: 'モデル:',
     sys_hostname: 'ホスト名:',
     sys_apply: '適用',
     sys_netmask: 'ネットマスク:',
@@ -500,6 +502,7 @@ var LANG = {
     sys_tab_console: '控制台',
     sys_heading: '系统设置',
     sys_ip: 'IP 地址:',
+    sys_model: '型号:',
     sys_hostname: '主机名:',
     sys_apply: '应用',
     sys_netmask: '子网掩码:',